Lumps.
The irritating thing about storing lithium is that it floats on the oil. That means unless you completely fill the jar, there's always a bit poking out above the oil, and that part starts oxidizing. The effect of which you can clearly see in the picture of this sample.

Click the source link for an interesting story about where this sample came from.

I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.